Industrial burner with recuperative means



July 26, 1966 F. o. HEss 3,262,484

INDUSTRIAL BURNER WITH RECUPERATIVE MEANS Original Filed Nov. 24, 1961 2Sheets-Sheet 1 July 26, 1966 F. o. HEss INDUSTRIAL BURNER WITHRECUYEHATIVE MEANS Original Filed Nov. 24, 1961 2 Sheets-Sheet 2 FIG.

INVENTOR. FREDERIC O. HESS Y/g'wm ATTORNEY.

United States Patent O 3,262,484 INDUSTRIAL BURNER WITH RECUPERATIVEMEANS Frederic 0. Hess, Skytop, Pa., assignor to Solas Corporation ofAmerica, a corporation of Pennsylvania Continuation of application Ser.No. 154,455, Nov. 24, 1961. This application Oct. 9, 1964, Ser. No.465,013 9 Claims. (Cl. 15S-7.6)

This is a continuation of application Serial No. 154,455 filed November24, 1961.

The present invention relates to burners and more particularly toburners for industrial purposes in which the burner is provided withrecuperative means to preheat the air being supplied thereto, and isdesigned to burn with a rich mixture to produce a protective atmospherein a furnace.

It is frequently necessary in the heating of metal to provide anon-oxidizing atmosphere around it. In such an atmosphere steel can beheated without scale and other metals without oxidation. Prior to thistime the metal has usually been heated in a muiile which was filled withthe desired atmosphere, or directly by burners fired with a rich mixtureof fuel and air. In the latter case the temperatures produced arerelatively low compared with those that can be produced with astoichiometric mixture of fuel and air.

It is an object of the present invention to provide -a burner which willoperate at a high temperature when burning a rich mixture of fuel andair.

It is a further object of the invention to provide a burner which willoperate efficiently and at a high ternperature with a rich mixture offuel and air, and one in which a portion of the partially burnedproducts of combustion are completely burned to preheat the air beingsupplied to the burner.

Another object of the invention is to provide a burner in whichincompletely burned products of combustion are drawn into a chamberforming part of the burner and 'burned to preheat the air.

The various features of novelty which characterize my invention arepointed out with particularity in the claims annexed to and forming apart of this specification. For a better understanding of the invention,however, its advantages and specic objects attained with its use,reference should be had to the accompanying drawings and descriptivematter in which I have illustrated and described a preferred embodimentof the invention.

In the drawings: A

FIG. 1 is a section through the burner, and

FIG. 2 is a view from the left of FIG. l.

In the heating of metal with a gas-air mixture of stoichiometricproportions, using a gas that requires nine parts of air to one of gas,for example, a relatively hot flame is produced, but the products ofcombustion will have an oxidizing effect on the metal when it reachestemperatures above about 1300 F. If the ratio of air to gas is changedto reduce the proportion of air, a nonoxidizing atmosphere is produced,but ordinarily the flame temperature is lowered, and as the ratio of-air is increased, a point is reached where the mixture will not burnwithout the addition of supplemental heat. The present burner isintended to operate with a gas-air ratio that will not ordinarily burnwith a hot flame, or -at all, without substantial preheating of the air.The atmosphere produced by the products of combustion with such a richmixture are such that steel can be heated to forging temperature Withoutthe formation of scale on its surface. The present burner Will burn sucha mixture at a temperature substantially equal to that obtained withstoichiometric proportions of fuel and air.

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Referring to FIG. l there is shown at 1 a furnace wall in which theburner is inserted and of which the front of the burner forms a part.The portion of the burner in the furnace wall includes a refractory cupblock 2 that has a cup-shaped depression 3 formed in the surface thereoffacing the furnace interior. Surrounding this cup block to form theremainder of the burner block there is provided a ring comprised of aplurality of segments 4 that are cemented to the cup block and to eachother. These segments are so formed that passages 5 extend through theblock to the rear face thereof. It is noted that both the cup block andthe segments 4 are provided with ridges 6 so that they will be held inaxial alignment, and so that the entire burner block will be heldaccurately in position in the refractory of the furnace wall.

Extending rearwardly from the composite burner block through theremainder of the furnace wall there is a cylindrical refractorystructure including two cylinders '7 and 3 of a dense refractorymaterial that are separated by a plurality of rings 41 of a porousrefractory. The rings and cylinders are held in position against theback of the burner block by means of a metal casing that is bolted tothe furnace wall. To this end there is provided a cylindrical part 11extending from the furnace casing. A lirst casing part 42, thatsurrounds rings 41, is bolted to a llange on 11, and a second casingpart 9 is bolted to the other end of part 41. The various parts 7, 41and 8 are cemented to each other, While cylinder 7 can be sealed, by abreakable cement, for example, to the back of the burner block. Cylinder8 is provided with an exhaust opening 12 that connects with a stack 13.The back of cylinder 8 is closed by a refractory disc 14 that iscemented in place in the end of the cylinder, but which is also held inposition by means of a metal cover 15. Cylinders 7, 41 and 8 form arecuperator chamber 16 in which are located the gas and air supply pipesthrough which fuel `and air are supplied tothe burner block.

The center .of the cup block 2 is provided with an opening 17 that isconcentric with the base of depression 3. A sleeve 18, which has anenlargement 19 on its rear end, is received in opening 17. Fastened tothe rear end of the enlargement is a tube 21 that extends rearwardlythrough an opening in disc 14 and cover 15. The right end of this tubeis sealed in gas tight fashion with respect to the cover by a seal ring22 which will permit movement between the tube and the cover. A fuel andair distributor tip in the form of element 23 is snugly received in thesleeve 1S. This element is provided with a plurality of radiallyextending gas passages 24 that are at such an angle to the axis of themember that they will discharge substantially parallel to the base ofthe depression 3. The exterior of element 23 is provided with aplurality of air passages 25 that are formed by helically extending ribs26 projecting from the outer surface of element 23. Fuel gas isdelivered to the passages 24 by means of a pipe 27, which pipe has aflange 28 extending radially from it for a purpose to be described. Theright end `of this pipe is threaded to a cap 29, which in turn is boltedto the cover 15. In this fashion the element 18 is positioned axially inopening 17. It is noted that a ring 31 is placed in the outer end oftube 21 to limit the movement of this tube with respect to pipe 27 andposition sleeve 18 axially with respect to element 23.

Air is supplied to passages 25 by means of a helical tube 32 whichsurrounds the tube 21. This tube is made of a high temperature alloy,and has a relatively thin wall. The left end of tube 32 is fastened tothe enlargement 19 so .that the tube is in communication with theinterior thereof. The outer or right end of tube 32 is indicated at 33as extending into a cap 35 to which the air connection from a suitablesource of supply can be made. A seal 3ft is provided between end 33 andcap 35 so that `the tube can move relative thereto. If it is desired, aninsulating refractory sleeve 36 can be placed around tube 21 inside thehelix of tube 32 to help along with the space between pipe 27 and tube21, to insulate pipe 27 from the heat. It is noted that the stack 13 issomewhat of the shape of a venturi, and is provided at or near its`throat with the discharge nozzle of a pipe 37 for air under pressure.

Additional air is supplied to the recuperator chamber 16 through theporous refractory rings 41. In order to insure that the additional airis introduced evenly around the chamber, each ring is provided aroundits outer surface with a recessed portion 43 to act as -a manifold. Eachmanifold is supplied with air through an opening 44 in casing part 42from separate air supplies 45, 46 and 47, respectively, which in turnare supplied by pipes shown as having conventional valves therein.

Raw gas, unmixed with air, can be supplied to the furnace chamberthrough the burner, if it is needed. This is accomplished by a tube 48that extends through pipe 27 with one end received in a hole in the endof element 23, and the other end held in place by a packing gland 49 inan extension 51 threaded into cap 29. The main supply of gas isintroduced through a pipe 52 into the extension 51.

When the burner is operating, fuel gas and air are supplied,respectively, through pipe 52 and a pipe 53 leading to fitting 35 in aratio `that has been determined to be necessary for the type of workbeing heated, and which is controlled by a ratio controller 54. Theburner will oper-ate with a fuel air ratio from stoichiometric to aratio in which there is an air deficiency greater than 50%. Since theburner is designed to be used with a deficiency of air, or what iscommonly known as a rich mixture, it will be so described.

Air flows through coil 32, where it is preheated prior to entering part19 on its way to passages 25. Flange 28 prevents the air `from travelingback along pipe 27. From these passages air is discharged into the cup 3to be thrown by centrifugal force along the surface thereof. Gas flowingthrough pipe 27 is discharged `from ports 24 to flow along the surfaceof the cup to mix with the air and burn. The base of cup 3 is providedwith a ridge, as best shown in the drawing, which creates enoughturbulence in the fiowing gas `and air to produce a piloting actionwhich will root the flames adjacent to the discharge ends of the gas andair ports. The burner will operate to heat the surface of the cup toincandescence and thereby direct radiant heat into the furnace. Heat isalso produced by the hot products of combustion.

In most furnaces there is some furnace pressure because of expansion ofthe gases of combustion. Such pressure will cause some of the hotproducts of combustion to flow backwardly through passages into thechamber 16 to be discharged through opening 12. Additional products ofcombustion can be drawn into chamber 16, and their flow controlled bythe aspirating effect of air supplied through tube 37. It is noted thatthe outer edge of the cup 3, radially inward of passages 5, terminatesin a substantially axial portion 3A. This portion directs the burninggases axially at this point into the furnace, and prevent them fromshort circuiting directly into passages 5.

Since there is a deficiency of air supplied to the burner, the productsof combustion will have a large percentage of unburned gas in them. Asthis gas is flowing through chamber 16 air, supplied through pipes 45,46 and 47 and flowing into chamber 16 through porous rings 41, will mixlwith the unburned gas and burn in the chamber. This secondary combustiontaking place around tube 32 adds to the heat of the products ofcombustion for preheating the `air supplied to the burner. Although itis possible to supply the air for secondary combustion .through asingle, wide, porous 3. ring, a more even distribution of air can beobtained throughout the chamber with a plurality of rings, since thecement between rings 41 forms, in effect, separate compartments.

Only sufficient air to burn enough of the unburned gas in the productsof combustion to obtain the desired preheat needs to be supplied throughthe porous rings. The volume of air can be regulated in any desired orconventional manner, such as a valve responsive to a ratio controllerfrom the gas supply, or the temperature of the preheated air, forexample, or manually. Because of the manifold sections 43, air will flowevenly into chamber 16 around its surface so that combustion can takeplace all around coil 32, thereby obtaining the maximum heating withouthot spots.

The amount of preheat that can be obtained for the combustion air willvary with the amount `of unburned gas in the products of combustion,determined by the air-gas ratio, and the volume of products ofcombustion drawn into chamber 16. The greater the deficiency of air froma stoichiometric mixture, the larger the percentage of unburned gas inthe products of combustion. Therefore, the richer the mixture thesmaller the percentage of products of combustion needed to obtain -agiven preheat temperature. The volume of products of combustion from theburner that is drawn back into the combustion chamber will vary with thefurnace draft or pressure, and with the aspirating effect of the airflowing through pipe 37. This air can be controlled in a conventionalmanner by a valve adjusted manually or in response to any desiredvariable such as the temperature of the preheated air, for example. Whenusing a fuel gas requiring an air-gas ratio of nine to one, with a fuelmixture of 41/2 to 1, a preheat ternperature of approximately 1300 F.yfor the combustion air can be obtained if 40% of the products ofcombustion are withdrawn through chamber 16, and the unburned fuelburned therein. This preheat temperature is sufficient to insure thatcombustion of such a rich mixture will take place, and at a temperatureonly one or two hundred degrees below that obtained with astoichiometric mixture. Burners of this type can be used for heatingsteel directly to forging temperature with a complete absence of scaleon its surface.

lf additional gas is needed in the furnace chamber for some reason, itcan be introduced through tube 48 extending axially through the burner.

From the above description it will be seen that the burner is aself-contained unit that can be supplied with any gas-air ratio to onehaving greater than 50% deliciency of air, thereby to produce in afurnace an atmosphere having desired protective characteristics. Thefeature of using a built-in recuperator for utilizing fuel that wouldotherwise be wasted to obtain the necessary preheat of the air does awaywith the necessity of auxiliary apparatus for this purpose. Thisself-contained, recuperative, atmosphere burner will reducesubstantially the cost and complexity of .metal heating equipment whenit is necessary or desirable to produce scale free Work.

An additional advantage that can be obtained with a iburner of this typeis the control of atmosphere and temperature distribution throughout afurnace. This can be accomplished by supplying different fuel-air ratiosto different burners, by varying the volume of products of combustionthat are withdrawn from different burners, and by varying the amount ofthe unburned gas in the products of combustion that is burnt. Theversatility in the manner that the present `burner can be operatedpermits the design and construction of superior furnaces.

While in accordance with the provisions of the statutes, I haveillustrated and described the best form of embodiment of my inventionnow known to me, it will be apparent to those skilled in the art thatchanges may be made in the form of the apparatus disclosed withoutdeparting from the spirit and scope of the invention set '5 worth in theappended claims, and that in some cases certain features of my inventionmay be used to advantage without a corresponding use of other features.

What is claimed is:

1. An indus-trial gas `burner comprising in combination: a burner blockhaving a face and a back and being provided with an opening extendingtherethrough, structure attached to said block forming a chamber havinga surrounding wall and an end wall with the back of said burner blockacting as said end wall thereof, means including pipes through whichfuel and air can be supplied to said burner block with said pipesterminating in discharge ports in said opening through which the gas andair are discharged to burn in front of said block, said pipes being atleast partially located in said chamber and supported by said structure,means to withdraw products of combustion, including unburned fuel, fromin front of said burner block and pass them through said chamber, saidstructure forming said chamber having a portion thereof which isprovided with a portion having a multiplicity of small openings, amanifold surrounding said portion, and means to supply air to saidchamber through said manifold and said portion of said surrounding wallin suflicient quantities to burn with said unburned fuel.

2. An industrial burner comprising in combination: a burner block havinga front and a back and a central opening and a plurality of `openingssurrounding said central opening extending from the front to the back,means attached to said block forming a chamber having walls back of saidblock with the interior of the chamber being in communication with saidplurality of openings, one wall of said chamber being provided with aplurality of ports around it, a pipe for a supply of gas extending tothe back of said block and terminating in discharge ports located insaid central opening, a pipe for a supply of air extending through saidchamber to the back of said block and terminating in discharge portslocated in said central opening, said discharge ports for gas and airbeing so directed that the gas and air will mix to be 4burned along thefront of said block, means through Iwhich gas and a deficiency ofair aresupplied to said pipes to be burned in front of said block, means toplace said chamber under reduced pressure thereby to withdraw productsof combustion from the front of said block through said plurality ofopenings, means including a part around said chamber to cover said portsand form a manifold, and means to supply air to said manifold andthrough the ports in said wall into said chamber to burn with theunburned gas in said products of combustion.

3. The combination of claim 2 in which the ports in said wall are formedas a piece of porous refractory material.

4. An industrial burner comprising in combination: a `burner blockhaving a front and a back adapted to be placed in a furnace wall andhaving a central opening 'and a plurality of openings surrounding saidcentral opening, a supply pipe for gas and a supply pipe for airextending from lback of said block to and terminating in said centralopening, the terminal ends of said pipes being provided with ports soshaped that the gas and air will mix as they are discharged therefromand burn across the front 'of said block, means forming a chamberattached to said block surrounding said pipes leading v to said block,said chamber having as a portion thereof a wall having a plurality ofsmall openings therein, a casing surrounding said portion of said Walland spaced therefrom to form a manifold, means to supply gas and air inproportions with a deficiency of air through said pipes to be dischargedthrough said central opening and burned in front of said block, means toplace said charnber under a reduced pressure thereby to withdraw aportion of the products of combustion through said plurality of openingsin said burner `block into said chamber, and means to force air intosaid manifold and through said portion of said wall into said chamber toburn therein with the unburned gas in the products of combustion.

5. In an industrial burner, a burner block provided with a centralopening and a plurality of openings around said central opening, asupply pipe for gas extending from the back of said burner lblock tosaid central opening, a supply pipe for air extending from back of saidburner block to said Central opening, said pipes being provided withdischarge ports in said central opening to direct the gas and air intomixing engagement, means attached to said block forming a chamber aroundsaid supply pipes with the interior of said chamber being incommunication with the back of said plurality of openings wherebyproducts of combustion can ow through said plurality of openings intosaid chamber, means to place said chamber under a reduced pressurethereby to draw a portion of said products of combustion through saidchamber, said means forming said chamber including a portion havingports therein, means surrounding the portion of the chamber having portstherein to form a manifold communicating with the ports and means toblow air into said manifold and through said ports into said chamber.

6. The combination of claim 5 in which said portion having ports thereinis formed of a porous refractory.

7. An industrial burner adapted to be inserted in a furnace wallcomprising structure havingva front face forming a portion of a furnaceWall and a back surface, said structure being provided With a firstopening extending from said front face to said back surface, and anotheropening extending from said front surface to said back wall, meansattached to said structure with the back surface of said structureforming one wall of said chamber, an element received in said iirstopening that is provided with a rst group and a second group ofdischarge ports, said groups of ports being designed to direct gas andair across said front face, a gas pipe extending through said chamberand terminating at said element .in communication with one of saidgroups of ports, an air pipe surrounding said gas pipe in said chamberand terminating in said element in communication with said other groupof ports, means to withdraw products of combustion from in front of saidfront face through said other opening into and through said chamber,said means forming said chamber including a portion thereof formed witha plurality of small passages, means t0 supply air to said chamberthrough said small passages, and a manifold surrounding said portion ofsaidchamber through which air is supplied to said passages.

8. An industrial gas burner adapted to be inserted in land form part ofa furnace wall including structure having a front face forming part ofsaid Wall and a back face, said structure being provided with a rstopening extending between said faces, a second opening extending betweensaid faces, means for-ming a chamber attached to said structure with theback face of said structure acting as one wall of said chamber, a gaspipe extending through said chamber and terminating in said firstopening, an air pipe extending through said chamber and terminating insaid rst opening with the air pipe surrounding the gas pipe, means toretard heat ow between said pipes, an element in said rst openingconnected to said pipes, said element being provided with ports todirect air and gas across said front face, means to draw products ofcombustion from beyond said front face through said second opening toand through said chamber, said means forming said chamber including aportion surrounding said air pipe through which air can flow into saidchamber to mix with the products of combustion therein and means toforce air into said l chamber through said portion.

9. An industrial burner adapted to be placed in a furnace wallcomprising structure forming a refractory chamber having end wallsseparated by a side wall, one of said end Walls being provided with acentral opening and a plurality of openings surrounding said centralopening, the outer face of said end Wall around said central openingbeing a surface along which combustion takes place, a gas pipe and anair pipe in said chamber, one end of each of said pipes terminating insaid central opening of said one end wall, the other end of each of saidpipes extending through the other end Wall, means at said end of saidpipes terminating in said opening including groups of ports throughWhich gas and air are discharged across said surface, means to placesaid chamber under a reduced pressure thereby to withdraw products ofcombustion from beyond said surface through said plurality of openingsto and through said chamber, said side wall including a section having aplurality of small openings through which air can be passed from theoutside to the interior of said chamber, a part covering and spaced fromsaid section to form a lmanifold on the exterior of said side wall andmeans to force air into said manifold and through said section to mixwith products of combustion in said chamber.

References Cited by the Examiner UNITED STATES PATENTS 2,992,676 7/1961Henwood 158-113 FOREIGN PATENTS 719,944 4/ 1942 Germany.

FREDERICK L. MATTESON, IR., Primary Examiner.

E. G. FAVORS, Assistant Examiner.

1. AN INDUSTRIAL GAS BURNER COMPRISING IN COMBINATION: A BURNER BLOCKHAVING A FACE AND A BACK AND BEING PROVIDED WITH AN OPENING EXTENDINGTHERETHROUGH, STRUCTURE ATTACHED TO SAID BLOCK FORMING A CHAMBER HAVINGA SURROUNDING WALL AND AN END WALL WITH THE BACK OF SAID BURNER BLOCKACTING AS SAID END WALL THEREOF, MEANS INCLUDING PIPES THROUGH WHICHFUEL AND AIR CAN BE SUPPLIED TO SAID BURNER BLOCK WITH SAID PIPESTERMINATING IN DISCHARGE PORTS IN SAID OPENING THROUGH WHICH THE GAS ANDAIR ARE DISCHARGED TO BURN IN FRONT OF SAID BLOCK, SAID PIPES BEING ATLEAST PARTIALLY LOCATED IN SAID CHAMBER AND SUPPORTED BY SAID STRUCTURE,MEANS TO WITHDRAW PRODUCTS OF COMBUSTION, INCLUDING UNBURNED FUEL, FROMIN FRONT OF SAID BURNER BLOCK AND PASS THEM THROUGH SAID CHAMBER, SAIDSTRUCTURE FORMING SAID CHAMBER HAVING